A sustained release formulation of recombinant human growth hormone (rhGH) will increase serum GH and IGF-I concentrations to normal concentrations when administered to adults with GH deficiency. Thirteen GH deficient adults (10 studied at the University of Virginia and 3 studied at New York University Medical Center) received a single subcutaneous injection of a long acting growth hormone preparation. Serum IGF-1 and IGFBP3 concentrations remained in the normal range for an average of 21 days. Clinical trials of this long acting GH formulation in GH deficient children are now underway in a multicenter study. The results of this study in GH deficient adults were presented at the Growth Hormone Research Society Meeting, London, November 13-16, 1996. This study is completed.